The Berkovich indentation loading curves of the initially only extraterrestrial available polymorphs of SiO2 are physically analyzed by applying the now well established FN-h3/2 plots for conical/pyramidal indentation...The Berkovich indentation loading curves of the initially only extraterrestrial available polymorphs of SiO2 are physically analyzed by applying the now well established FN-h3/2 plots for conical/pyramidal indentations, in view of determining the phase-transition onset forces, indentation energies, and transition energies. Two phase-transitions of synthesized Stishovite yielding 2 polymorphs (one of them is Seifertite) with these properties are characterized. A third post-Stishovite polymorph is safely projected for higher load indentation. Both of them are now available at room temperature on earth for further investigation and the projected third of them is waiting. The published “pop-ins” had to be removed by self-evident repair of the force-depth curve. The meaning of published “pop-ins” is elucidated, apparently for the first time. The reasons for them and their avoidance are manifold. They are not materials’ properties but mechanical artefacts. Published pop-ins are not at all connected to phase-transitions, despite theoretical considerations claiming elastic-plastic conversion at the start of “pop-ins”. Spherical indentation analyses before them are obsolete. Final support is inter alia that one of the two new MgO twinning transitions is within a published “pop-in excursion”. The putting of a pop-in arrow at smooth loading curve without discontinuities is criticized, as the transfer between chemically different phases is neither phase transition nor “pop-in”. The polymorph’s onset forces, their energies and their endo- or exo-thermic phase-transition energies are reported. The development of the Stishovite, post-Stishovite and MgO polymorphs is mechanochemical analyzed. High pressure polymorph energetic properties are important for the earth’s sub mantel investigations and for public safety of technical materials such as MgO for constructions, or covered superalloys for e.g. airplanes, turbines, etc. Breakage and catastrophic cracks are more easily initiated at polymorph interfaces, the onset and transition energies must be above the highest possible mechanical and thermal stress for their being safe.展开更多
A theoretical “drift-flux based thermal-hydraulic mixture-fluid coolant channel model” is presented. It is the basis to a corresponding digital “Coolant Channel Module (CCM)”. This purpose derived “Separate-Regio...A theoretical “drift-flux based thermal-hydraulic mixture-fluid coolant channel model” is presented. It is the basis to a corresponding digital “Coolant Channel Module (CCM)”. This purpose derived “Separate-Region Mixture Fluid Approach” should yield an alternative platform to the currently dominant “Separate-Phase Models” where each phase is treated separately. Contrary to it, a direct procedure could be established with the objective to simulate in an as general as possible way the steady state and transient behaviour of characteristic parameters of single- and/or (now non-separated) two-phase fluids flowing within any type of heated or non-heated coolant channels. Their validity could be confirmed by a wide range of verification and validation runs, showing very satisfactory results. The resulting universally applicable code package CCM should provide a fundamental element for the simulation of thermal-hydraulic situations over a wide range of complex systems (such as different types of heat exchangers and steam generators as being applied in both conventional but also nuclear power stations, 1D and 3D nuclear reactor cores etc). Thereby the derived set of equations for different coolant channels (distinguished by their key numbers) as appearing in these systems can be combined with other ODE-s and non-linear algebraic relations from additional parts of such an overall model. And these can then to be solved by applying an appropriate integration routine. Within the solution procedure, however, mathematical discontinuities can arise. This due to the fact that along such a coolant channel transitions from single- to two-phase flow regimes and vice versa could take place. To circumvent these difficulties it will in the presented approach be proposed that the basic coolant channel (BC) is subdivided into a number of sub-channels (SC-s), each of them being occupied exclusively by only a single or a two-phase flow regime. After an appropriate nodalization of the BC (and thus its SC-s) and after applying a “modified finite volume method” together with other special activities the fundamental set of non-linear thermal-hydraulic partial differential equations together with corresponding constitutive relations can be solved for each SC separately. As a result of such a spatial discretization for each SC type (and thus the entire BC) the wanted set of non-linear ordinary differential equations of 1st order could be established. Obviously, special attention had to be given to the varying SC entrance or outlet positions, describing the movement of boiling boundaries or mixture levels along the channel. Including even the possibility of SC-s to disappear or be created anew during a transient.展开更多
文摘The Berkovich indentation loading curves of the initially only extraterrestrial available polymorphs of SiO2 are physically analyzed by applying the now well established FN-h3/2 plots for conical/pyramidal indentations, in view of determining the phase-transition onset forces, indentation energies, and transition energies. Two phase-transitions of synthesized Stishovite yielding 2 polymorphs (one of them is Seifertite) with these properties are characterized. A third post-Stishovite polymorph is safely projected for higher load indentation. Both of them are now available at room temperature on earth for further investigation and the projected third of them is waiting. The published “pop-ins” had to be removed by self-evident repair of the force-depth curve. The meaning of published “pop-ins” is elucidated, apparently for the first time. The reasons for them and their avoidance are manifold. They are not materials’ properties but mechanical artefacts. Published pop-ins are not at all connected to phase-transitions, despite theoretical considerations claiming elastic-plastic conversion at the start of “pop-ins”. Spherical indentation analyses before them are obsolete. Final support is inter alia that one of the two new MgO twinning transitions is within a published “pop-in excursion”. The putting of a pop-in arrow at smooth loading curve without discontinuities is criticized, as the transfer between chemically different phases is neither phase transition nor “pop-in”. The polymorph’s onset forces, their energies and their endo- or exo-thermic phase-transition energies are reported. The development of the Stishovite, post-Stishovite and MgO polymorphs is mechanochemical analyzed. High pressure polymorph energetic properties are important for the earth’s sub mantel investigations and for public safety of technical materials such as MgO for constructions, or covered superalloys for e.g. airplanes, turbines, etc. Breakage and catastrophic cracks are more easily initiated at polymorph interfaces, the onset and transition energies must be above the highest possible mechanical and thermal stress for their being safe.
文摘A theoretical “drift-flux based thermal-hydraulic mixture-fluid coolant channel model” is presented. It is the basis to a corresponding digital “Coolant Channel Module (CCM)”. This purpose derived “Separate-Region Mixture Fluid Approach” should yield an alternative platform to the currently dominant “Separate-Phase Models” where each phase is treated separately. Contrary to it, a direct procedure could be established with the objective to simulate in an as general as possible way the steady state and transient behaviour of characteristic parameters of single- and/or (now non-separated) two-phase fluids flowing within any type of heated or non-heated coolant channels. Their validity could be confirmed by a wide range of verification and validation runs, showing very satisfactory results. The resulting universally applicable code package CCM should provide a fundamental element for the simulation of thermal-hydraulic situations over a wide range of complex systems (such as different types of heat exchangers and steam generators as being applied in both conventional but also nuclear power stations, 1D and 3D nuclear reactor cores etc). Thereby the derived set of equations for different coolant channels (distinguished by their key numbers) as appearing in these systems can be combined with other ODE-s and non-linear algebraic relations from additional parts of such an overall model. And these can then to be solved by applying an appropriate integration routine. Within the solution procedure, however, mathematical discontinuities can arise. This due to the fact that along such a coolant channel transitions from single- to two-phase flow regimes and vice versa could take place. To circumvent these difficulties it will in the presented approach be proposed that the basic coolant channel (BC) is subdivided into a number of sub-channels (SC-s), each of them being occupied exclusively by only a single or a two-phase flow regime. After an appropriate nodalization of the BC (and thus its SC-s) and after applying a “modified finite volume method” together with other special activities the fundamental set of non-linear thermal-hydraulic partial differential equations together with corresponding constitutive relations can be solved for each SC separately. As a result of such a spatial discretization for each SC type (and thus the entire BC) the wanted set of non-linear ordinary differential equations of 1st order could be established. Obviously, special attention had to be given to the varying SC entrance or outlet positions, describing the movement of boiling boundaries or mixture levels along the channel. Including even the possibility of SC-s to disappear or be created anew during a transient.
